Update README.md

Clean up the wording and don't mention Tipsify; instead move the
references to the Tipsify to the source code (one day we might switch to
a different algorithm).

src/vcacheoptimizer.cpp

@@ -4,6 +4,8 @@
 #include <cassert>
 #include <vector>
 
+// This work is based on:
+// Pedro Sander, Diego Nehab and Joshua Barcz. Fast Triangle Reordering for Vertex Locality and Reduced Overdraw. 2007
 namespace meshopt
 {